The pair was riding out of bounds when they found themselves trapped in a gully with a high avalanche probability. Grouse Mountain has received near record-breaking amounts of snowfall during the Christmas period. The father and son were lucky. However, officials are now issuing a warning to all skiers and snowboarders to stay within marked boundaries on the hill. "They're very lucky," said Erik Bowkett, Grouse's operations manager. "When you go into an area that hasn't had avalanche control, there's a very high risk of being injured or killed."